1. Field of the Invention
This invention generally relates to a plastic bellows container for a viscous fluid. More particularly, this invention relates to a plastic bellows container that can substantially completely discharge the viscous fluid contained in the bellows container.
2. Description of the Prior Art
Plastic bellowslike or bellows containers for various uses are conventionally made by a blow molding means into various configurations and sizes. Such plastic bellows containers can be produced rather cheaply such that plastic bellows containers are usually disposed of after a single use.
Most conventional plastic bellows containers are contracted vertically along their axis to discharge the viscous fluid content. Bellows are provided along the side wall of containers such that the bellows "close" when the plastic containers are contracted along the vertical axis of the containers and usually "open" back when the contracting forces no longer apply.
When a plastic bellows container is molded by means of blowing a plastic material ("blow molding"), the farther away the portions of the bellows of the container are from its central vertical axis, the thinner they are made. Thus, the outermost portions or ridges of the side bellows are formed the thinnest and the innermost portions or ridges of the side bellows are formed the thickest. Therefore, when such a plastic bellows container is contracted to the fullest in an attempt to push out "all" the viscous fluid content, the "overlapping" thick innermost portions or ridges of the side bellows create "space" or "void" along the axis of the bellows container, keeping the top portion of the plastic bellows container from contacting the bottom portion of the bellows container. Thus the viscous fluid content of the plastic bellows container in the void cannot be discharged to the last portion. Such space or void in the bellows container unavoidably holds a portion of the fluid content. The plastic bellows container with a remainder of the viscous fluid content is usually disposed of together with the plastic container as trash, which is waste of the content and uneconomical.
Here, the terms "space" and "void", which will be generally replaced by the term "dead space" hereinafter, generally mean the space or void created by the overlapping (innermost ridges of) bellows of a bellows container when the bellows container without any fluid content is "fully" contracted along its axis.
There have been introduced a number of plastic bellows containers in an attempt to discharge the viscous fluid contents in the bellows containers to a maximum degree. Japanese Utility Model Laying-Open Publication No. 4-7478(1992) (filed Jan. 23, 1992 in the name of Dai-Nippon Printing Co., Ltd. ) discloses a plastic bellows container having a bottom plate with an inner protrusion which protrudes into the container such that the protrusion enters the "otherwise (without the protrusion)" created dead space in the bellows container when the bellows container is fully contracted and helps discharge the viscous fluid content from the "dead space".
It requires an additional manufacturing step to mount such a bottom plate having an inner protrusion as disclosed in said Publication No. 4-7478 onto a bellows container since the bottom plate with the protrusion cannot possibly be formed together with the rest of the plastic bellows container in a single blow molding process, thus unavoidably and considerably pushing up the manufacturing cost. Further, the inner protrusion on the bottom plate much decreases the total capacity of the bellows container, which is a considerable drawback.
Japanese Utility Model Laying-Open Publication No. 59-168350(1984) (filed Apr. 28, 1983 in the name of Kureha Chemical Industries Co., Ltd. and Kureha Plastics Co., Ltd.) discloses a plastic bellows container with an inwardly rising or depressed bottom such that the rising bottom enters such otherwise created "dead space" as well as the neck portion of the bellows container when the bellows container is fully contracted, helping discharge the viscous fluid content in the otherwise created dead space and even in the neck portion of the bellows container.
Japanese Utility Model Laying-Open Publication No. 59-174474(1984) (filed Mar. 16, 1983 in the name of Corpo Co., Ltd.) discloses a plastic bellows container whose bottom is depressed to the inside of the bellows container. The configuration of the depressed bottom substantially corresponds to that of the "dead space" otherwise made in the bellows container such that the "dead space" may be eliminated by the depression and the viscous fluid content in the otherwise created "dead space" of the bellows container is discharged or pushed out when the bellows container is fully contracted.
Japanese Utility Model Laying-Open Publication No. 60-169143(1985) (filed Apr. 19, 1984 in the name of Haruyasu Takamizawa et al.) discloses a plastic bellows container the bottom of which is depressed into the bellows container so that the depression enters the otherwise generated "dead space" and the neck portion of the bellows container when the bellows container is fully contracted, pushing the viscous fluid out of the "dead space" and the neck portion of the bellows container to a maximum degree.
These plastic bellows containers disclosed in said Publication Nos. 59-168350, 59-174474 and 60-169143 are all moldable in a single blow molding process. However, if the bottoms of these containers are to be made rigid or thick enough so that the protrusions or depressions may function as designed, the bellows side walls of the bellows containers become excessively rigid or thick. Such excessively rigid or thick bellows side walls make it hard for users to contract the containers conveniently. In addition, when the bellows side walls are made "too" rigid or thick, void or "dead space" to be created in those bellows containers by the thick overlapping bellows, when the bellows containers are fully contracted, unavoidably become "too" large, requiring to make the size of such protrusions or depressions correspondingly larger to fill the increased "dead space". Then the inside utilizable volume or capacity of such bellows containers is destined to decrease correspondingly because of such protrusions or depressions, which is a contradiction and a considerable drawback.
On the other hand, if it is attempted to make it easy or convenient for users to contract or use the bellows containers, and if it is attempted to make such "dead space" smaller, by molding the bellows side walls thin enough, then the bottoms of the plastic bellows containers will be made too thin or soft, thus the protrusions or depressions of the plastic bellows containers will not function properly or as desired since such thin protrusions or depressions will be easily deformed by the pressure from the viscous fluid content.
In addition, in order to eliminate "dead space" as completely as possible, such protrusions or depressions are usually made horizontally wide. When a plastic bellows container with a wide protrusion or depression on the bottom is to be charged with a highly viscous fluid, the wide protrusion or depression on the bottom of the bellows container often obstructs complete filling of the bellows container with the viscous fluid as the upper edge of the wide protrusion or depression is too close to the innermost ridges of the bellows around the bottom, and the gap between the upper edge of the protrusion or depression and the innermost ridges of the bottom bellows is too narrow, preventing the air trapped between the side wall of the protrusion or depression and the side wall of the bellows container from effectively escaping.
In order to solve those problems considerably, it is required to prepare very complicated and very well designed (thus expensive) molds and to use "higher skills". The manufacturing processes will be more complicated as well and thus the productivity will be much deteriorated. The resulting products or plastic bellows containers will become unavoidably much more expensive, which is a great disadvantage.
Japanese Utility Model Laying-Open Publication No. 56-100347(1981) (filed Dec. 28, 1979 in the name of Diesel Machines Co. Ltd.) discloses a plastic bellows container with an inner depressed bottom, whose bellows side wall is tapered such that the bellows do not "squarely" overlap one on another, or the innermost ridges of the bellows do not vertically overlap one on another. The tapered bellows side wall helps make "dead space" considerably smaller in the bellows container when the bellows container is fully contracted. The round shaped depression provided on the bottom of this bellows container partially fills the "dead space" which is created in the bellows container anyway.
The tapered plastic bellows container disclosed in said Publication No. 56-100347 certainly makes such "dead space" smaller, and the round depression on the bottom will partially eliminate the space made inside the container, however, even this bellows container cannot totally eliminate dead space, and the dead space in the neck portion of this bellows container remains unattended. And the drawbacks set forth earlier remain unsolved with this plastic bellows container.
Accordingly, it is an object of the present invention to provide a "cheap" plastic bellows container which can easily push out substantially all the viscous fluid content in the bellows container.
It is another object of the present invention to provide a cheap plastic bellows container capable of easily discharging substantially all the viscous fluid content and still easily and completely filling out even with a highly viscous fluid.
It is still another object of the present invention to provide a cheap plastic bellows container capable of easily discharging substantially all the viscous fluid content and still providing a "large" capacity.
It is another object of the present invention to provide cheap plastic bellows containers of various configurations, including bellows containers with a single bellows, which are capable of discharging substantially all the viscous fluid content.
It is a further object of the present invention to provide a cheap plastic bellows container that can keep the content fresh and without deterioration by air and contamination.